Spaceflight Insider

Latest images of Pluto from New Horizons show complexity, contrast

Image Credit: JHUAPL / NASA

Laurel Kornfeld

June 17th, 2015

A recent series of images captured by the New Horizons’ Long Range Reconnaissance Orbiter (LORRI ) from a distance of about 30 million miles (150 million km) reveal Pluto as a complex world with highly contrasting bright and dark regions, leaving scientists puzzled. These are just the latest images snapped on the road to Pluto – a journey which should culminate in a flyby of Pluto, slated to take place next month.

Taken between May 29 and June 2, they are considered to be the best photos of the dwarf planet taken to date. The images show both very dark and very bright regions, sometimes separated by areas with an intermediate level of brightness.

Image Credit: NASA

The strong variation in color is consistent with images of Pluto taken by the Hubble Space Telescope, which also show a high level of color contrast.

The New Horizons team released four separate images, each presenting a different “face” of the planet during its 6.4-day rotation period. Depicted from left to right, they were taken when Pluto’s central longitude was at 17, 63, 130, and 243 degrees, respectively.

In addition to showing the longitude, each image lists the distance of the spacecraft from Pluto when the photo was taken, in both miles and kilometers, plus the number of days until closest approach.

The mission team also created a movie from images taken by LORRI from May 28-June 3, showing the planet rotating on its axis.

Dramatic variations in color and brightness are evident in both the movie and in the still photos of Pluto rotating.

Near the equator, one particularly dark area makes Pluto appear non-spherical when it rotates along the limb, but that appearance is false, as previous data confirms the small world is almost perfectly round.

“Even though the latest images were made from more than 30 million miles away, they show an increasingly complex surface with clear evidence of discrete equatorial bright and dark regions – some that may also have variations in brightness,” noted principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado.

A month out from the flyby of Pluto, preparations are being made for this historic event are picking up. Photo Credit: JHUAPL / NASA

“We can also see that every face of Pluto is different, and that Pluto’s northern hemisphere displays substantial dark terrains, though both Pluto’s darkest and its brightest known terrain units are just south of, or on, its equator. Why this is so is an emerging puzzle,” he said.

Stern believes the bright and dark spots are evidence of a highly nuanced and complex surface.

Answers to the puzzle will start coming in early July, when New Horizons begins doing spectroscopy, which will play an important role in identifying surface composition.

Image Credit: JHUAPL / NASA

Like previous LORRI images, these photos underwent a process known as deconvolution to sharpen them and bring out details.

Used since April, this process has unveiled dramatic markings across Pluto’s surface, including a bright area at one of its poles that appears to be a polar cap.

If confirmed, the existence of a polar cap would make Pluto one of only three worlds orbiting the Sun to host such caps, the other two being Earth and Mars.

Because deconvolution can produce false artifacts, mission team members will compare these with closer images taken over the next few weeks to distinguish real from false features.

On June 14, New Horizons underwent a small course correction via a 45-second thruster burn to assure optimal approach for the flyby. Its velocity was adjusted by only 52 centimeters per second, based on the latest radio tracking data and on recent measurements of the distance to Pluto taken during optical navigation over the last few weeks.

Had the maneuver not been done, the spacecraft would have missed its aim point by 470 miles (755 km) and would have arrived 84 seconds earlier than planned.

If found necessary, another, similar course adjustment may be done on June 24. New Horizons is now less than 22 million miles from Pluto, which equals less than 100 times the Earth-Moon distance.

Hazard-search data taken May 29–30 and June 5 by LORRI using long-exposure images has not revealed any new moons, rings, or other potential dangers to the spacecraft. Another search begins on June 15; its results will be reported around June 25.

Approach Phase 3 (AP3) begins the last week in June and runs until seven days before the flyby. While optical navigation images will continue to be taken during this phase, the transition will mark the beginning of mapping both Pluto and Charon, including more in-depth studies of surface composition and color variation. Study of atmospheric patterns will commence, and New Horizons will measure the solar wind, high energy particles, and dust particle levels near the Pluto system.

“It’s exciting – come and watch as New Horizons turns points of light into a newly explored planetary system and its moons!” Stern encouraged.

With less than 30 days to go before the encounter, the mission team has embarked on a new public outreach effort, holding weekly updates on New Horizons every Tuesday at 11:30 AM EDT on NASA TV. The updates are rebroadcast several times on Tuesdays, at 3:30 PM, 7:30 PM, and 11:30 PM EDT, and at 7:30 AM on the following Wednesday morning.

On June 12, the mission team released an hour-long documentary, “The Year of Pluto”, which is available for viewing on YouTube.

The latest LORRI images, currently dated June 13, are also available for viewing online.

Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.